Spinosa, Salvatore (2026) A multidisciplinary approach to characterizing atmospheric aerosols from natural sources as well as desert dust and volcanic emissions. [Tesi di dottorato]

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Abstract

Atmospheric aerosols affect climate, air quality, and cloud processes, but their impact remains difficult to quantify because similar column-integrated optical signals can arise from particle populations that differ markedly in size, composition, and mixing state. This non-uniqueness is especially critical in the Central Mediterranean, where an urban–marine background frequently overlaps with transported natural aerosol (Saharan dust, volcanic aerosol, and wildfire smoke). This thesis addresses the problem by exploiting the synergy between long-term sun–sky photometry and vertically resolved lidar profiling, complemented by targeted instrumental developments to strengthen measurement capability. A climatological reference is established through an 8-year AERONET analysis (2016–2023) at ten Italian sites. Seasonal and geographical variability is assessed using AOD at 440 nm and the Ångström exponent (440–870 nm), and supported by inversion products (SSA, complex refractive index, and volume size distributions) to interpret absorption and dominant size regimes. The analysis highlights systematic contrasts between regions dominated by anthropogenic fine-mode aerosol and areas more frequently influenced by coarse particles due to marine aerosol and Saharan dust intrusions. Two case studies demonstrate the value of time- and range-resolved observations under complex conditions. First, fresh volcanic ash from Mount Etna (21 February 2019) is characterized using the multi-wavelength polarization AMPLE lidar and the VALR-ML retrieval framework to identify ash layers and derive quantitative ash parameters, including mass concentration levels relevant to aviation thresholds. Second, a multi-layer episode over Naples (2–5 June 2025) is reconstructed by combining lidar profiles and AERONET products with satellite/model support (CAMS/EUMETSAT, DREAM8b, HYSPLIT), enabling discrimination of volcanic, dust, and smoke contributions and interpretation of their evolving overlap in altitude and time. Overall, the thesis shows that vertical profiling substantially reduces the ambiguity inherent to column-only information in multi-layer and mixed scenarios, and that improved acquisition/detection solutions (e.g., compact dual-mode acquisition and exploratory near-IR single-photon detection) support more flexible and transportable observational strategies for future deployments.

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